Aerosol dispensers have been available for a number of years for the application of hair sprays and other personal care products, as well as for paints, lubricants, insecticides and a multitude of other liquid products. LP gas (liquified petroleum gas) is sold over the counter in the U.S., Japan and other countries in such aerosol type dispensers.
In earlier times within the aerosol industry, "Freon" blends were widely used as propellants, principally because they were not flammable and were relatively nontoxic. After it was discovered that "Freons," when released into the atmosphere, migrated to the upper stratosphere and contributed to the depletion of ozone the U.S. Environmental Protection Agency (EPA) and similar agencies in other countries banned the further use of "Freon" propellants. This forced aerosol packagers to seek alternative propellant systems.
Among the newer propellants are the various hydrocarbons, consisting of propane, butane and isobutane and mixtures thereof. However, such hydrocarbon propellants are extremely flammable, and are in the chemical class known as volatile organic compounds.
In some countries such as Japan, these hydrocarbon compounds either singly or in mixtures are used not just as propellants, but as fuels, primarily for cooking. Thus cans of these aliphatic hydrocarbons with special valves thereon adapted to engage components of a cook stove to control the flow of the highly pressurized gas, are sold for household use.
Just as there is a problem in the aerosol packaging industry in the disposition of the used aerosol containers, particularly for large scale commercial users, so too is there a problem with the disposition of these spent fuel cans. After the cooking gas within the can has been essentially used up, the container retains some residual hydrocarbon gas. Since the cooking gas hydrocarbons, which act as both product and propellant as viewed from the perspective of those in the aerosol industry, constitute a flammable gas, the container from which they came is considered hazardous waste. For ease and simplicity, the term cooking gas as used herein is intended to mean LP gas, i.e., liquified petroleum gas; namely, C.sub.3 -C.sub.4 hydrocarbons and blends thereof of varying vapor pressures.
There is a growing concern worldwide about the discharge of these gases into the atmosphere, whether they are used as propellants for other products or by themselves as fuels. In addition, Japan's regulatory system prohibits the reliquification of residual LP gas. There is a need therefore for a means to compact down the spent cans of cooking gas and to capture any residual cooking gas remaining within without reliquefying the gas. This invention provides a unique way to extract the residual cooking gas for recovery and possible re-use and permits the safe compaction of the empty can for recycling.